What strategies are used to reduce engine friction and improve efficiency?

Engine friction reduction strategies include: Low-tension piston rings, DLC (diamond-like carbon) coated components, roller cam followers replacing sliding contacts, variable oil pump (reduced parasitic losses), low-viscosity oils with friction modifiers, offset crankshaft (reduced piston side thrust), bearing design optimization, electric water pump and vacuum pump, thermal management for faster warmup, and precision machining for reduced clearances. Collectively these can reduce friction losses by 20-30%, improving fuel economy by several percent.